Electrical testing device



Jan-'12, 1960 K. K. KENNEDY l ELECTRICAL TESTING DEVICE Filed May 13, 1955 v J .Il

/NVENTOR K K. KENNEDY ATTORNEY ELECTRICAL TESTING DEVICE Kenneth K. Kennedy, West Caldwell, NJ., assignor to Bell f Telephone Laboratories, Incorporated,4 N.Y., a corporation of New York Application May v13, 1955, Serial No. 508,104 6 Claims. (Cl. Z50-27) New York,

This invention relates generally toelectrical testing delvices and more particularly to such devices for testing invention is inthe nature of such a testing circuit whichl can monitor the electrical condition of a component or circuit and which will operate selectively for various conditions detected thereby.

lGenerally, the exemplarly embodiment of the present invention comprises a circuit for detecting various levels vof voltage on a conductor. The circuit is subjected continously to the conductor potential and includes a number of voltage and current responsive circuit elements wherei United States Patent by a dilferent operative condition of the circuit will exist for different voltage levels detected.

The main object of the invention is to improve the reliability of Vsuch testing devices and to enable rapid action at ahigh level of reliability.

The testing circuit illustrative of the invention includes at least two electron` discharge devices each having two principal conducting conditions, namely, oit and on. The bias circuits for each device are arranged such that a change of conduction condition in each device will be caused by a different level of voltage applied thereto. Also, there is circuitry interconnecting the devices whereby if a certain one thereof changes its condition it will prevent. theV other one from so doing underl certain circumstances.

Particularly, two dual-triode tubes are arranged in respective voltage comparator circuits whereby under Anormal conditions both will be in condition A (for instance both conducting on side 1 and non-conducting on side 2V). Bach is provided with a bias circuit on side l and an input circuit on side 2. The input circuits are interconnected to the conductor whose potential is to be tested. The respective bias circuits are arranged such that the first tube will ilip over if the tested potential exceeds a rst specified amount and such that the second tube will ip over if the tested potential exceeds a second specified amount greater than the first amount. Circuit means interconnects the two bias circuits and is effective whenever the second tube ps over to prevent the first tube from so doing'. Each tube is arranged to operate a may be grounded. A hundred steering relays D00 to D99 1 2,921,191' Patented Jan. 12, 1960 ICC ' AC00, etc.

Three possible conditions are of interest with respect to connectors DC00, AC00, DC99, AC99, etc. One condition is where none of these connectors is operated; a second condition is where only one of them is operated; and, a third condition is where two or more are operated.

The vacuum tube COT is arranged to cause the operation of relay C0 whenever one or more connectors DC00, etc. is (or are) operated and to prevent the operation of relay C0 when no connectors DC00, etc. are operated.

The vacuum tubes DCOT and SCOT are arranged in interconnected circuits whereby relay SCO is operated and relay DCO is released when only one connector DC00, etc. is operated and whereby relay DCO is operated and relay SCO is released whenever two or more connectors DC00, etc. are operated.

Atest conductor C is connected into the left grid circuits of tubes SCOT and DCOT and into the grid circuit of tube CGT. This conductor C is arranged such that with no connectors operated it will be at about 50 volts direct current (all voltages etc. are direct current) below ground potential, to be referred to as minus 50 volts, and with only one connector operated it will be at about 24 volts direct current above ground potential, to be referred to as plus 24 volts, and with two or more connectors operated it will be at plus 55 volts or more.

These various voltage levels on conductor C come about through the agency of a potentiometer circuit wherein the value of a resistance section is changed depending upon the number of connectors operated. The main potentiometer circuit extends from ground to the negative side of battery B2, out the positive side of battery B2 (about plus volts), through resistance R10 to conductor C1, through the amount of resistance RX which is the eifective resistance between conductors C1 and C, to

Aconductor C, through resistance R2, to the negative side of battery B1 (about minus 50 volts), the positive side of which is grounded. A resistor RD00, RA00 to RD99, RA99 is associated with each connector DC00, ACOt) to DC99, AC99 and is connected between conductors C and C1 whenever the associated connector is operated. With no connectors operated, there is practically infinite resistance RX and conductor C stands at about minus 50 volts, the value of battery B1. With only one conductor operated, RX is of a value determined by the value of one ofthe resistances RD99, etc., and is such a value as will cause conductor C to stand at about plus 24 volts. With Vtwo connectors operated, two of the resistances RD99,

Vthesecircumstances, tube COT is non-conducting, tubes SCOT and DCOT are non-conducting in their left halves and conducting in their right halves, and relays C0, DCO and SCO are released. Resistance R10 is used merely as a current limiting impedance to protect the battery B2. in

case a false ground should get onto conductor C1.

The potentiometer comprising resistances R1 and R3 extends from plus 130 volts to negative battery B1 (minus 50 volts) and is so Yarranged that the lower terminal of the varistor V1 is maintained at about plus 24 volts. The

faQ-anim held at about plus 24 ivolts, thenpperterminal cannot s0 more positive than that. This means that vthe leftgrilof tube SCOT cannot ybe driven more positive thanabout plus remain conducting on. its rightside (keeping .relay SCO released) whenever more than one connector is operated.

24 volts regardless of how high the conductor C may go positively, l

The potentiometer comprising resistances R4 yand R5, l

extending from plus 130 volts to minus 50 vo1ts,.arranges ,to maintain the right grid of tube .'DCOllat about plus 40 volts. f

y The potentiometer comprising resistances R6 land'R?,

1 ,extendingfrom plus 130 voltsto minus `5() volts, arranges yto maintain the right grid offztube SCOT at Vabouttplus l2 volts. With the right-hand part of tube DCOT'Aconducting, there is a `current liowing through the Jgas diode T; its upper electrode stands at about plus5 Y volts and its lower electrode at about plus ,8O volts. 7.5 yvolt drop intube T is always about the same.

v Y The *tubes SCOT and DCOT are arranged Ainf-voltage comparator circuits; that is, they will conduct on the right halves when the right grids are Ymore .positive than Mthe left ones and will conduct-.ori the left halves when t kvto its right side when conductor C drops to plus 24 volts or lower and tube SCOT will flip backl to its right side when conductor C drops to minus 50.volts.

yIt is not desirable for tube SCOT to be operated on its left side when conductor C goes to plus 55 volts or higher f because then both of the relays DCO and SCO would be operated. It is desired that relay SCO operate only to indicate a single connector operated (conductor C 4at plus 24 volts). It is desired that relayDCO operate to l,indicate more than one connector operated (conductor `C at plus 55 volts or higher).

Tube COT will conduct (to operate relay CO) when one or more connectors is or kare operated (conductor C at plus 24 volts or higher). In order'to prevent relay SCO from operating when and if conductor C should rise to plus 55 volts or higher,

the circuit at the right plate of tube DCOT (plate resistor "RS) is arranged to increase the positive voltage on the rvlower terminal of tube T byabout 40 volts whenever the tube DCOT flips over fromthe right to the left side. This will cause the upper electrode of tube T to assume a potential of about plus 45 volts since the tube drop in tube T is about 75 volts. Since the varistor V2 becomes low impedance when its lower or arrow terminal is more positive than its upper terminal (upper is at plus l2 volts ,and lower is at plus 45 volts), the right grid of tube VvSCOT will be driven more positive than plus 24 volts (actually nearly to plus 45 volts) whenever tube DCOT 'flips from' its right side to its left side. vSince the left grid of tube SCOT cannot go more positive than about plus 24 volts due to the action ofvaristor Vil, thetube TAS-COT will be forced to remain conducting on its'right vvside whenever tube DCOT` flips to its left side; This'in- 'sures that only relay DCO will be operated (along with `relay kvCOf'of course) when conductor C goes to plus 55 Y volts or higher.

Tube COT conducts and operates relay CO when one or more connectors is orare operated; tube SCOT ips from right to left to operate relay SCO when only'one connector is operated; tube DCOT .iiips fromright to left operate relay DCO when two or more Ac onnectors are operated; and, the'interconnecting circuits Abetween the Y'right sides of tubes DCOT and'SCOT'foi'ce-tube SCOT lto What is claimed is:

Resistance R9 decouples the clamping action of varistor V1 from the other tube input circuits.

It may be desirable tov .inject some delay into the operation of relay SCO in order to insure that relay SCO does not falselyoperate, to, givean lerroneous indication,

. due to some time ydelayi n operatinga second cenneetor.

Such means for delaying the operation'of relay 4,SCO are wellknownin the art. i

The resistance lamp L, in the cathode circuit of tube COT, is used to widen `-therarige 'of' grid voltages over which suicient plateeurrent will vflow through tube COT, to operate relay CO, without having excessive grid currents with high grid voltages. The variable resistance (increases with increases of current due to higher temperatures) of-the lamp will `also ltend .to .reducegrid Acurrent flow gbecause, yas the Vvgrid voltage.v goes up (more positive), thecathcde vvoltage will ,tend `'to follow more closely than with a iixed resistance. y

lt' is t0 vbei understood that the .above-descrbed-.arrangcments are merely .illustrative ofthe application of the principles of the linvention. Numerous Lother-arrangements may be devised by thosesflilled inthe art without departing fromths Spirit fanfl'segpsfgfthe invention .1, An electrical tstugdevise .crimpfiisne a first slactron discharge device operable only bye iirst Avoltagelevel applied thereto, a second electron .discharge device operable by said lirst or a( second voltage level Aapplied thereto, means for applying a .voltage .of said first level to both devices concurrently, and'voltage responsive circuit means interconnecting said two devices and controlled by*v an operation of said-first vdevice `foripreventing vthe Y operation of said second device .when .both -have applied concurrently thereto said firstlevel voltage.

2. An `electrical testing device compri*sing alii-st Epair of electron discharge tube :paths in .a circuit including one normally non-conducting .electron .discharge path, another normally eondncting electron `discharge path and va lir'st circuit means including an impedance. common to vsaid rst pair and arranged'topreseribe aiirst level-of t voltage which if'appliedv to `sailtirstpair will reverse the Yconducting and non-conducting conditions of..said first pair; a second pairof electrondischarge .tube paths .in a circuit including alirst normally non-conducting electron discharge path, a second normally conductingv electron discharge path and a second circuit means including yan impedance common to said second pair and .arranged to prescribe a second level `of .voltagesuch @hat .either Isaid rst or a second level of' voltage if appliedto said second pair will reverse the keondrlctiirg Yand non-.conducting Aconditions of .said .second pain-means efer appl-.Yigg a -voltage of said Afirsvtlevelto b oth pairs-concurrently; and ,a voltage responsive circuit. intereonnecting Isaid yfirst-.zand Y.said second 4circnit lmeans and controlled Aby-a reversal `of current conditions in said '.fiirst .pairwfor .forcing said second pair to v4remain normal. Y

3. An electrical Ltesting device comprising'a first pair of control grid vacuum tubes-in v aflirst voltageeomparator -circuit including a common '.loa'd impedance` and bias circuits for prescribing a Ltir-st level Vofgrid voltagewhich if applied to said first pair will reyerse the normalcurrent conditions in respective tubes, a secondpair'pf control rgrid Yvacuum tubes .in ,a second VQltagecOmparatQr cirfsecond pair'will reverse thegnormal current ,conditions in respective tubes, means for applying a voltage offSaid sponsive circuit interconnecting ,said'cbias :circuits Y of said pai-IS and Y controlled by areversal vvof .current conditions in said first pair for forcing said second pair to remain normal.

4. An electrical testing dev ice comprising a first double triode vacuum tube in a first voltage comparator circuit including a common cathode impedance, a first triode section having a grid bias circuit normally biasing the grid below cut-oli and arranged to prevent the grid from being driven more positive than a first voltage level, a second triode section having a grid bias circuit normally biasing the grid in the conducting region below said first voltage level; a second double triode vacuum tube in a second voltage comparator circuit including a common cathode impedance, a first triode section having a grid bias circuit normally biasing the grid below cut-off and arranged to permit the grid to be driven more positive than said first voltage level, a second triode section having a grid bias circuit biasing the grid in the conducting region approximately as positive as said first voltage level; means for applying to both first triode section grid circuits a voltage more positive than said first level; and a voltage responsive circuit interconnecting said second triode sections and controlled by a reversal of current conditions in said first tube for forcing said second tube to remain normal.

5. An electrical testing device comprising at least two detecting means, one detecting means operable only by a first electrical condition when subjected thereto, another detecting means operable by said first or a second electrical condition when subjected thereto, means for subjecting both detecting means concurrently to said first electrical condition, and means controlled by an operating of said one detecting means for rendering inoperable the other when both are subjected concurrently to said first electrical condition.

6. An electrical testing device comprising at least two voltage responsive detectors, one detector operable only' by a first voltage level applied thereto, another detector operable by said first or a second voltage level applied thereto, means for applying said first voltage level to said detectors concurrently, and means interconnecting said two detectors and controlled by an operation of said one detector for rendering inoperable the other when both have applied concurrently thereto said first electrical con1 dition.

References Cited in the tile of this patent UNTTED STATES PATENTS 2,290,992 Peterson July 28, 1942 2,428,126 Nicholson Sept. 30, 1947 2,486,391 Cunningham Nov. 1, 1949 2,572,912 Bucher Oct. 30, 1951 2,603,123 Loukomscky et al July 15, 1952 2,620,400 Snijders 1 Dec. 2, 1952 2,650,332 Bordewieck Aug. 25, 1953 2,684,479 Hill et al July 20, 1954 2,708,254 Macaulay et al. May 10, 1955 

